The present invention relates generally to engine thermal management and more particularly to a method of optimizing engine thermal management as a function of electrical load management, fuel economy and emissions using an electric waterpump, a flow control valve, and an electric cooling fan.
Engine cooling systems typically have many functions on vehicles. Cooling systems may remove excess heat from the engine, maintain a constant engine operating temperature, increase the temperature in a cold engine quickly, and provide a means for warming a passenger compartment.
There are two types of automotive cooling systems: air and liquid. Air cooling systems use large cylinder cooling fins to remove excess heat from the engine. Liquid cooling systems circulate a solution of water and/or coolant through water jackets. The coolant collects excess heat and carries it out of the engine. Liquid cooling systems offer several advantages over air cooling systems, including more precise control of engine operating temperatures, less temperature variation inside the engine, reduced exhaust emissions because of better temperature control, and improved heater operation to warm passengers. As such, liquid cooling systems are typically used on automobiles today.
Liquid cooling systems generally consist of the engine water jacket, thermostat, water pump, radiator, radiator cap, fan, fan drive belt (if necessary) and necessary hoses.
The water pump is typically an impeller or centrifugal pump that forces coolant through the engine block, intake manifold, hoses, and radiator. It is driven by a fan belt running off the crankshaft pulley. The spinning crankshaft pulley causes the fan belt to turn the water pump pulley, pump shaft, and impeller. Coolant trapped between the impeller blades is forced outward, producing suction in the central area of the pump housing and pressure in the outer area of the housing. Since the pump inlet is near the center, pressurized coolant is pulled out of the radiator, through a lower hose, and into the engine. It circulates through the engine block, around the cylinders, up through the cylinder heads, and back into the radiator.
Cooling system fans pull air through the core of the radiator and over the engine to help remove heat. Typically, a belt or an electric motor drives the fan. Electric fan switches use an electric motor and a thermostatic switch to provide cooling action. When the engine is cold, the switch is open. This keeps the fan from spinning and speeds engine warm-up. After warm-up, the switch closes to operate the fan and provide cooling. An electric engine fan saves energy and increases cooling system efficiency by only functioning when needed. By speeding engine warm-up, it reduces emissions and fuel consumption.
One problem with commercial water pumps is that the flow rate of coolant is controlled by engine speed, not by the amount of cooling that the engine needs. Therefore, there is no way to optimize engine thermal management using a mechanical water pump alone. Thermal management during the engine warm-up stage is typically controlled by adding a thermostat between the water pump and radiator that restricts the flow of coolant to a radiator. In this way, the engine can warm up quickly in cold start conditions. However, engine thermal management after an engine is warmed up is strictly controlled by the engine speed, which causes the water pump to pump fluid cooled by the radiator through the engine. Thus, for example, when an automobile leaves a highway and enters city traffic, the engine speed and radiator cooling capability may not be adequate to cool the engine block in a timely manner. This could result in damage to vital engine components.
One way to optimize engine thermal management is to use an electric water pump. The pumping rate of the electric water pump could be modified as necessary to control fluid flow through an engine. For instance, in cold start up conditions, the electric water pump may be set at a slow pumping speed. As the temperature increases, the pumping speed may be correspondingly increased to a certain flow rate to control engine temperature. When used in conjunction with an electric fan and a flow control valve, the engine thermal management may be optimized.
It is thus an object of the present invention to provide an electric water pump, a flow control valve and an electric cooling fan optimization strategy that incorporates engine thermal management, electrical load management, engine emissions, and fuel economy.
The above and other objects are accomplished by providing a system that automatically adjusts the flow rate through the engine cooling system via a water pump and/or adjusts the cooling rate of an electric fan motor and/or adjusts the flow rate of coolant through the flow control valve to optimize engine thermal protection and corresponding emissions and fuel economy as a function of electric load management. A powertrain control module electronically coupled with the electric pump, flow control valve and electric fan determines when, and at what rate, the pump, a flow control valve and an electric fan are utilized based on various engine parameters. The powertrain control module controls various other system parameters in correlation with the electric pump, flow control valve and electric fan.
Other objects and advantages of the present invention will become apparent upon considering the following detailed description and appended claims, and upon reference to the accompanying drawings.